America’s accelerating sovereign debt crisis, much reduced force structure in Korea and low public opinion support for more interventions badly constrain its ability to meet its alliance commitments here, and many other places.

The probability of major U.S. assistance, on which Korea has built its security for two generations, is diminishing. Analysts need to be far more forthright about this. Call it the end of empire, retrenchment, or imperial overstretch, whatever, but the “age of austerity” is no longer deniable:

1. U.S. Forces in Korea (USFK) are now 28,500 servicemen, the smallest ever. In my experience, Koreans expect America would land a large army to fight a conventional war like last time. Yet America’s total land forces comprise less than 600,000 soldiers today, and 10 years of the global war on terrorism has worn down the force. Any ground war will be born mostly by the ROK army this time.

2. U.S. tactical nuclear weapons were removed from Korea 20 years ago, after the Cold War. Given North Korea’s nuclear program, the ROK elite have been hinting recently that they might like to see them come back or at least discuss it. The U.S. has rejected this.

3. The Combined Forces Command (CFC) is still scheduled for abolition. CFC places wartime authority in Korea over both U.S. and Korean forces with a U.S. general. This is widely viewed in Korea as a signal of U.S. commitment to the South’s defense. Because of the North’s recent behavior, Seoul has made noises about retaining this, but the U.S. has held firm that it too will go.

4. U.S. public opinion surveys from the Chicago Council of Global Affairs find only 40 to 45 percent of Americans actually want to fight in South Korea if a war comes: “Americans also show an inclination to take a hands-off approach to confrontations between North and South Korea.” This should not surprise anyone given American exhaustion from its war on terrorism.

Consider the current Libya intervention. It is mostly an “inside-the-Beltway” affair; U.S. public opinion support for it is tepid. As a result, U.S. involvement is very light. Obama is badly constrained by huge U.S. public reticence to fight yet another big war ― which a Korean conflict would probably be. Libya is far more likely to be the U.S. model in Korea than a re-run of 60 years ago.

5. The USFK is being relocated away from the demilitarized zone (DMZ) to Pyeongtaek. Seoul is the obvious target in any serious conflict, so USFK’s placement between the North Korean army and its ally’s capital signaled strong American commitment, both reassuring the South and deterring the North.

Any combat at the DMZ would immediately pull in U.S. soldiers. Emotionally provocative images of American servicemen fighting and dying would enrage U.S. public opinion and help catalyze or “chain-gang” U.S. participation in an otherwise unwanted and potentially very costly war. The USFK DMZ “tripwire” firmed up the U.S. commitment to the fight. U.S. forces south of Seoul reduce American exposure, giving the White House “wiggle room” it did not have before.

6. Even if all of the above were irrelevant however, the elephant in the room that casts doubt on all U.S. alliance commitments (not just Korea) is its crushing deficit and debt. America now borrows $1.5 trillion per annum. This is the largest peacetime borrowing in U.S. history (and only matched once ― in World War II). It represents a staggering 10 percent of GDP, 35 percent of the total budget ($4.2 trillion), and 150 percent of the South’s entire GDP.

America’s publicly-held debt is now $9 trillion, around 50 percent of which is held by non-Americans. These budget constraints will place major limits on any U.S. use of force in the future. Again, the current Libya campaign should be seen as a model for what U.S. war in the age of austerity will look like ― hesitation, buck-passing to allies and international organizations, “leading from behind,” no “boots on the ground,” and cost-efficient airpower.

The only way to close that massive $1.5 trillion gap is to either cut spending or raise taxes. Because the signature policy position of the Republican Party for decades has been “no new taxes,” spending must be cut. And no one seriously believes $1.5 trillion in savings can be found without huge defense cuts. Social Security, Medicare and Medicaid, plus defense, comprise 70 percent of the U.S. budget. (Interest on the debt, which cannot be cut, is 11 percent; “discretionary spending” is 19 percent.)

The choice between defense and Social Security, Medicare and Medicaid is an absolutely classic guns-or-butter trade-off. This budgetary mathematic all but mandates major U.S. retrenchment, unless Americans are willing to dramatically lessen their entitlement expectations to make room for defense. And to no one’s surprise, polling of Americans finds that 60 percent do actually favor major defense cuts in order to “save” Social Security, Medicare and Medicaid.

Americans, if they must choose, want checks for grandma more than they want aircraft carriers. This is why Michael Mullen, chairman of the U.S. Joint Chiefs of Staff, argued recently that the U.S. budget deficit is now the single biggest threat to U.S. national security. And the Sustainable Defense Task Force, organized by several members of Congress, does in fact recommend U.S. cuts in Korea.

The U.S. is badly overextended, risking bankruptcy, and exhausted after a decade of war. To forestall a semi-imperial crack-up like the Soviet Union or the Austro-Hungarian Empire, major cuts in places where American do not wish to be (Iraq, Afghanistan, Pakistan, Libya) and places Americans believe can afford their own defense (Western Europe, Japan, Korea) are likely. Retrenchment is coming; American allies ignore this at their peril.

Dr. Robert Edwin Kelly is an assistant professor at the Department of Political Science and Diplomacy, Pusan National University in Busan. He can be reached at robertkelly260@hotmail.com.